Elliptical wings an empennage, warping, trimming, flying and things like that...

[Matt Piatkowski]

Hello,
I have read Brett's essay about trimming, flying, hinging, "warts", warping, elliptical wings, piloting, rolling, and yawing in square maneuvers, etc.
I have found this thing accidentally, searching for hinging, after I published my previous message about the outside flap tab (wart)and some of you responded.

I am pleased to announce that now I understand why my colleagues in Poland fly the F2B planes with elliptical wings and tail surfaces (empennage) and many of RTF laminate F2B planes from Ukrainian and Russian factories are "ellipticals".

The elliptical wing is more efficient aerodynamically as it has less induced drag than the wing with square tips. More efficiency == less battery or/and less fuel used in flight.
When the balsa, "classical" wing is hand-made from scratch by cutting ribs, gluing spars and sheeting, etc., there is always some warp no matter what fixture is used.
Like Brett stated in his essay, the build-up balsa wing with square tips has the warp effect simply more pronounced than the balsa build-up elliptical wing.
In other words: the elliptical wing is less prone to exhibit warp-related aerodynamic disturbances.

This assumes of course that the builder is experienced and knows how to build wings well. This also assumes that a decent quality and light balsa is available - an interesting subject these days.

The laminate wings from the F2B model factories are built in molds and they are practically warp-free. If those wings are elliptical or semi-elliptical, they are simply "aerodynamically clean" and the stunt planes having such wings do not need long and laborious trimming to limit or get rid of the warp effects.

As I understand these things better now (thanks Brett!), my next full-size stunt plane (eParrotXL2) will have the build-up balsa elliptical wings and tail surfaces.

I will also flight test my brand new laminate LA-4e in Poland in July. This large F2B plane has semi-elliptical wings so I expect it will fly well without warps and warts.

Happy Flying in US Nats!
M

 

[Avaiojet]

Hello,
I have read Brett's essay about trimming, flying, hinging, "warts", warping, elliptical wings, piloting, rolling, and yawing in square maneuvers, etc.
I have found this thing accidentally, searching for hinging, after I published my previous message about the outside flap tab (wart)and some of you responded.

I am pleased to announce that now I understand why my colleagues in Poland fly the F2B planes with elliptical wings and tail surfaces (empennage) and many of RTF laminate F2B planes from Ukrainian and Russian factories are "ellipticals".

The elliptical wing is more efficient aerodynamically as it has less induced drag than the wing with square tips. More efficiency == less battery or/and less fuel used in flight.
When the balsa, "classical" wing is hand-made from scratch by cutting ribs, gluing spars and sheeting, etc., there is always some warp no matter what fixture is used.
Like Brett stated in his essay, the build-up balsa wing with square tips has the warp effect simply more pronounced than the balsa build-up elliptical wing.
In other words: the elliptical wing is less prone to exhibit warp-related aerodynamic disturbances.

This assumes of course that the builder is experienced and knows how to build wings well. This also assumes that a decent quality and light balsa is available - an interesting subject these days.

The laminate wings from the F2B model factories are built in molds and they are practically warp-free. If those wings are elliptical or semi-elliptical, they are simply "aerodynamically clean" and the stunt planes having such wings do not need long and laborious trimming to limit or get rid of the warp effects.

As I understand these things better now (thanks Brett!), my next full-size stunt plane (eParrotXL2) will have the build-up balsa elliptical wings and tail surfaces.

I will also flight test my brand new laminate LA-4e in Poland in July. This large F2B plane has semi-elliptical wings so I expect it will fly well without warps and warts.

Happy Flying in US Nats!
M

M,

I won't disagree with anything you're saying, in fact, I agree!!

However, you might want to read the following. I designed an Elliptical wing some years ago and some commentary was a bit negative from one of the Experts.

Here's one reply I received from Kieth Trostle. Kinda talked me out of building a model around the wing I designed. You can see the CAD drawing and the Thread at this link.

https://stunthanger.com/smf/cfc-graphics/elliptical-wing-design-and-layout!/

Here's Kieth's comments,

"Other than the desire to build an elliptical wing airplane, I would not recommend building one of these.  Yes, I still have plans that could be used to build this thing, but time would be better spent on something else.  Also  Also, that white airplane had a tricycle gear which in my opinion now is totally unnecessary on a stunt ship and adds unnecessary weight and does not help with the landings and takeoffs and is a detriment to the appearance of the airplane flying through the pattern.

Also, this combination of numbers, though giving me some success was based on a composite of a number of designs from the early 60's.  By the standards of today for what make a good stunt ship, the flaps are too small at 15%, the horizontal tail is too small at about 15% and the tail is too short.  Yes, I built a replica of my Focke Wulf several years ago and placed 2nd at the VSC when I flew it and later placed 1st at the Classic event at the Nats (all in 2008), but that winning flight was in ideal weather conditions., I have talked to another top builder/flier from that 60's/70's period who had a fairly successful elliptical wing design and he told me he was more satisfied with straight tapered wing versions of that airplane. My opinion is that they look nice, but they are not suited for serious competition stunt."

[Brett Buck]

Thank you for the very flattering comments on my article!   I do not promise or guarantee 100% accuracy, but I try my best...

   I think your thought process is very familiar, but has led you into a strange set of conclusions. There may be a small improvement in tolerance for warps, but the elliptical wing is vastly more difficult to build straight in the first place, and in any case, you can't expect to come up with a good airplane with *any* significant warp/misalignment, no matter what shape the wing might be otherwise. Even a straight-taper wing (with it's 4% or so hypothetical increase in the induced drag over an elliptical wing) seems to be extremely difficult to build sufficiently straight and sufficiently stable with normal techniques, elliptical even more so.

   Your conclusions are interesting, and there may be a kernel of truth there, but with all due respect, I think you are, overall, *misunderstanding* the nature of stunt and stunt development - psychology. You are approaching it from the standpoint of an engineering exercise, which is not a bad starting point, and assuming everyone else is doing the same, in this case, it is a microscopic difference in induced drag (4-5%, maybe, over a straight taper). They aren't - there are far more powerful drivers, like, Igor's Max Bee and the Yatsenko Shark seem to fly good, win all the local contests and sometimes the US NATs, so why not do it like they are doing it?

   Just as an observation, you seem to be chasing a tiny theoretical advantage and, just perhaps, missing a lot of more important and much more prosaic issues, like your ability to build a straight conventional wing - which is no mean feat under normal circumstances. I think it might be solving a problem you don't have - a few percent more performance in some parameter is likely to be completely swamped by other effects of trim and power that, maybe, you haven't fully mastered.

   Of course I don't know for sure, I have never seen you fly, but most, the vast, vast, majority of people would be better served by sticking with entirely conventional designs that are as simple as possible, to keep the challenges of trim, power, construction, well within their capabilities, and only seek design "improvements" when they run into limitations. I can tell you beyond a shadow of a doubt that even something as rudimentary as a Skyray 35 and a 20FP is capable of winning most expert contests in the USA, when you exclude the usual Top 5 contenders, and flying legitimate 500-point patterns (figure, 1000-point in FAI).  There definitely are limitations to it, but, no insult or slight intended, most people will not be able to find them - because they will have other issues that prevent them from reaching the full potential.

   As always, this is just advice, and it is intended to be helpful and perhaps point out some factors you are missing. I am particularly attuned to this particular problem, because *I used to have the same problem that I think you have*, that is, that solving a series of theoretical engineering and design problems will result in success - when the problems were far more prosaic matters of trim, power, and piloting.

    Brett   

[Trostle]

[quote author=Brett Buck link=topic=59635.msg615806#msg615806 date=1623880575

... a straight-taper wing (with it's 4% or so hypothetical increase in the induced drag over an elliptical wing) seems to be extremely difficult to build sufficiently straight and sufficiently stable with normal techniques, elliptical even more so.

 You are approaching it from the standpoint of an engineering exercise, which is not a bad starting point, and assuming everyone else is doing the same, in this case, it is a microscopic difference in induced drag (4-5%, maybe, over a straight taper).

   Just as an observation, you seem to be chasing a tiny theoretical advantage

    Brett
[/quote]

I have taken some liberties by selecting specific quotes from Brett. Given that there may be a slight theoretical advantage in reduced induced drag ("4-5%") of a stunt design with an elliptical wing over a straight tapered wing only considers the airplane portion of the system.  The modern day stunt ship represents nothing but a lot of drag with its 18%, + or -, wing section, exposed landing gear/wheels, large flaps and elevators, and the canopy/cockpit which only serves for appearance points and perhaps some perceived advantage to have some fuselage side area.  The real gorilla in the room is line drag which might account for 30 to 40% of the total drag of the airplane/line system.  To reduce induced drag of the airplane by "4-5%" really reduces the total system drag by a few percentage points.  There are many other factors to be concerned about regarding power train and airplane trim as suggested by Brett to reach some modicum of optimum performance.

I like the appearance of elliptical wing stunt ships.  My experience with some of my own elliptical designs, though comparatively limited to flying in only local contests at the time, then converting the same numbers to a straight tapered wing design showed me no advantage with the elliptical wing.  (That straight tapered wing design placed in the top five at three Nationals).

Reducing induced drag is important in full scale aircraft when range and endurance are important design factors.  Possible reduced fuel load to complete the pattern by a couple of percentage points serves little value in a stunt design.

I think there is an underlying reason we do not see any preponderance of true elliptical wing stunt ships winning in the major stunt contests.  They do not fly any better in my humble opinion.

Keith

[Howard Rush]

One could get the same induced drag advantage by increasing aspect ratio of a trapezoidal wing a bit, but we don’t, because we fly planes with aspect ratios that are about optimal.

[Air Ministry .]

Trying to find the picture of the effilander like plank / elip. tip Spit. Was ' the Best ' when you needed two hands & kick heels into grass center , in a ' breeze ' to stop being pulled downwind .

Ah Ha ! . gottit . The 2.7 mm wire ' K ' horn arms  could get overpowered downwind in 20 knots at ground level , on entry. Delayed , on squares .twanging a .018 laystrate line territory . Line stretch .
directly downwind from level . Off to the side was fine . You can see the elevator ears . Rock hard Q grain New Ginea 1/4 sheet stab. & flaps . No flight traumas or prangs .Untill the pushrod end snapped
from being mauled in forced ajustments , Inverted wing over pullout with Irvine 40 RE & 10 x 4 black Tornado prop . The Usual G 51 10 x 6 ditto , could get overpowered & drift slightly , in a gale .
Flying the full pattern . More annoying than worrying . Mainly vertical in the rounds . Hence my current 5/32 wire flap horns . filed tappered to 1 / 16 Th in. 2 or 2 1/2 inch rearward .



Pretty much a cross of ony Eifflaender,s diesel gold tropy winner 7 Compostellas 4 stroke ship .



YAW Stability good . Hence it behaved well , non divergent . though elevator ears I think maintained steerabilty / manadgeable controll loads .

Belows the ' Full elip ' .



Invasion Stripes make warp detection / straightning visual across from the tip . Otherwise packers at spar & T E taped on , with a few chordwise straight edges .

You get a bit more span & perhaps chord , for the same A/R . And have to be carefulkl to maintain full % airfoils at the ends . Dont thin them .

[Air Ministry .]

I think THIS ' clipped wing tip ' Eliptical is likely the best starting point , to maintain area , compactness , transportablity . Easier to keep straight & adj. leadouts a ton easier .



Scale, thats at the rib past the flap end, on the big picture . Urtnowskis 90 is the same , with 5/8 in. extra chord, and differant tips .
----------------------------------------------------------------------------------------------------------------------------------------------------


Eifflaender, free bird . plan. British Nats Gold trophy winner . A bit of wind over there , so suitable for breezy flying .

the T-Bird wing is similar to a T-Bolts . which works out well , exact scale . And dosnt need a fancy L E or elliptical spars . Plus a ' N ' has the clipped ips ( with a wider centersection )


One can fudge the flaps on a Spit 90 , so theyre consant chord initially - 6 inch. almost . Joe adamushko'd be the one to question for Elip. performance . Having built ' one or two ' .

[Matt Piatkowski]

Good Morning,
The way I see the entire "elliptical thing" right now is as follows:

1. Elliptical wing and empennage are more difficult and time-consuming to build compared to the square tips wing and empennage when the classical construction method is used
    (balsa ribs, balsa/spruce spars, balsa sheeting, etc.)

2. Even if extraordinary care is taken selecting the balsa available, it will be nearly impossible to select and use the wood having SYMMETRICAL properties. "Symmetrical" means that
    the balsa density, grain type, and grain distribution are such, that top and bottom of, say, wings sheeting, react the same way to bending while sheeting is being glued. In my
    opinion, the symmetrical balsa properties are nearly impossible to achieve for ANY balsa-built wing, elliptical or not.

3. Considering the above, there will ALWAYS be some warp, somewhere.

4. The warp may have a form of slightly twisted tips, wavy LE or TE, local "collapse" of the sheeting between ribs, deviations caused by sanding...anything.

5. Warp has the WORST aerodynamic effect when the tips are twisted

6. Warp in tips of elliptical wings has a smaller aerodynamic effect (thanks again, Brett for making this crystal clear) than warp in square tips wings.
    It is, therefore, easier to fix the parasite rolling induced by this warp, tweaking the flaps when elliptical wings are used.

7. Balsa reacts to moisture by expanding. Spray painted doped Silkspan or/and Polyspan covered outside balsa skin do not provide 100% moisture protection from the inside.
    When bare balsa on the inside of wings is exposed to humidity, the humidity-induced balsa expansion builds up and will warp the wing either more or in some new, weird way.
   
8. Laminate structures of RTF, Ukrainian, and Russian F2B models, based on 0.8 -1.0 mm. balsa sandwiched between glass-fiber or/and carbon-fiber fabric saturated with
    thermally stabilized epoxy do not react to humidity. Balsa's expansion due to humidity and temperature is RESTRICTED much better than in the case of Silkspan/Polyspan
    coverings. Such wings and empennage are HUMIDITY NEUTRAL and keep the original, molds made, shapes.
   
    Interestingly enough, some Ukrainian and Russian manufacturers started using AIREX structural foam instead of Balsa wood. AIREX is HUMID NEUTRAL and
    ISOTROPIC.
   
    This is, in my opinion, the breakthrough in the development of the HUMID NEUTRAL and WARP FREE stunt/F2B models but....

9. No stunt/F2B model in the world is free of the TEMPERATURE EXPANSION warp effects. With summers becoming hotter, there is no way to avoid the structural material
    expansion that may (and probably will) affect the roll, pitch, and yaw aerodynamic behavior.

10. Laminate models are LESS prone to temperature expansion warps than the Balsa-made, Silkspan/Polyspan covered, and spray-painted models.

11. All the above may (and probably will) matter for the top ten, maybe fifteen best stunt/F2B pilots in the world. For the advanced pilot like myself (920-950 FAI points per
      pattern and ~ 480 AMA points per pattern) the warp effects, assuming the wings, elliptical or not, are not twisted, say, five degrees, are not really important.
      What is important is pattern consistency in flying the model that had slightly warped wings that were fixed by tweaking the flaps and were constructed in a reasonable
      time.

Conclusion: you want to fly the pattern better being a very good pilot, say, AMA/PAMPA expert level? Buy something from Ukraine and Russia and use contra TMT or
                 GAU/D. TMT contra power plant with electronics and battery is (and always will be)  about 60 grams heavier than the geared contra GAU/D power plant with
                 electronics and battery. Some of my colleagues in Poland use now full-size stunt/F2B planes weighing 950 grams fully finished but before mounting the contra power
                 plants. This gives the total RTF weight of the plane =1700-1750 grams. A very light large plane is, unfortunately, a little FLEXIBLE plane and maybe a little WEAK plane that
                 bounces here and there during wind gusts.
                 Like with everything else in this strange sport we try to achieve perfection but it is not possible.

Happy Summer flying and do not forget about your plane protection from the sun when it sits on a tarmac for three hours in the 90 deg. plus weather.
Best Regards,
M
   

[Howard Rush]

5, 6 maybe not. Midwing anomalies affect pressure distribution over more of the wing. Full-scale airplanes, according to Gary Letsinger, would have ailerons farther inboard if flaps weren’t in the way.

[Air Ministry .]

I told Wilbur , i told Orrville , if men were supposed to fly , they woulda been born with feathers ! .

Re Ailerons , Howard . One or two did havem in'board .


seafire 47 .Hernán Martinez . http://www.apuca.com.ar/Fotos/Fotos3.htm

appear to be the same plane . Cannae geton the pictures . Notta my computor .

Theres a Detroiter Ellip. wing here . Should satisfy Brett , as it should warp in the sun .       Seafire MK47 von Yves Fernandez .  https://www.fesselflug.ch/content/modellbau/werkstatt/seafire-mk47-.html

Thought the modern plastic coverings were pretty impervious to heat beformation ?? . If you accept EXCELLANCE as attainable . Optimum current tech / or traditional . Been around for years ! 
one minute flaw would be short of 'perfection ' so its more a theological term . Or delusion of mediocratists , or regard supurlatives as everyday terms . Obvviously they only apply to my 61 Bonneville ,


a few round case Ducatis , and natural species ! . 

Been wondering regarding tapered wooden masts Vs Aluminium . Presumably hyper buck tapered . A hand  whittled mast can be contrived to flex as required , and its greater bulk may actually offer aerodynamic / flow ADVANTAGES ,

Hence say , a Timber  [ balsa ? ] laminate , spruce edged spar may be configured to accept deflection advatageously . Which I understood was a fundamental of Beringers Concept . No interspar webs to rigidify load absorbtion .

Heres a link to a horedous quality picture of one of Beringers  Spits . Perhaps a Sheeks derivative ? Used one at the British Nats a few times, around 1980 . One ST 46, one 40 FS maybe ??
https://stunthanger.com/smf/nostalgia-30/beringer-spitfire/msg461088/#msg461088

[Air Ministry .]

Theres a story from Aston Martin  ( the real Aston Martin / David Brown days , where after the new Grand Prix regulations are announced ,
Ebenezer Von Ebanhorst , the designer of the DBR1 front suspension ( & chassis ? )
  dissapears into his office with his three foot sliderule .
To emerge three days later to announce , It will not be neccesary to build a 1.5 litre supercharged engine .
Weyer & co announce ' We Knew That ' .

Carrol Shelby LeMans Numero Uno . 1959 .



As ten minutes mulling it over revealled 4500 Vs 1500 Supercharged favoured the former .

Ho Kay. Might Work . Yves Ving ,
Fudge , Im sure you can click on the pictures of the wing structure , at the link above ,
Hern'an's terrorplane .



Calculus is usefull to back up / anylise theorys . Rather than define them . Otherwise it implies FINITE . Which rather obscures excellance ,
which implies visionary or inspired work , Nevertheless they co-exist . Though infinity ( the absolute ? ) by its nature , cannot be defined .

Doing a elliptic leading edge , you maybe wanna do a pine or whatever plug , cut to accomodate them . Overlength . Damp & mould them , maybe from 2 mm / . 077 in. sheet strips  , to 5/8 Sq or whatever you need ,
Tends to open out after a few days off the plug . so the outer plug continuation will gett excess end curve to compensate . Detroiter a full sheet , flat , at the rear , will maintain alignment ,
a sheet with the inside edge trimmed would be a L E option . sat flat on 2 x 4 blocks on a flat surface would automatically jig the jigger .

Harder to think about than do , so getting stuck in , and learning from the experiance , is the best starting point .  Urtnowskis 90 wings available as Drg.s & lasert cut rib set , 3/8 steel rod jigged to build .
Comes out around 58 span , sans elip tips . So would getya airborne . You may even like it . Believe he did a detroiter big Spit too . 

[Air Ministry .]

 
Sie sind hier: Fesselflug.ch » Modellbau » Werkstatt

Seafire MK47 von Yves Fernandez


I see web site Agentignen ; the Seafire MK47 fabioulous modèle from Hernan Martinez ( designer motorcycle).
The original wing construction is on tubing carbon dia 26 ; RC longeron system. I thing this is heavy
And not rationnal .I use my construction, 3X10 pine wood reduce and end 3X6 ;I BEAM construction.
I beam is light,speed realisation and perfect géométrical.
The problème with semi scale model is the weight ; big nose ,big modèle.
The détachable wing mécanismous + 60 Grs ( 2oz) + 10 grs Rudder +10grs Stabilo.
The landing gear complète with weel ; two pieces 100 grs ( 4 oz)
I use for glued the cyanolacrylate very fluid ZAP"CA (red bottle) ; with this glue i bringt half time for
Built one model. For the planqing i use white glue or Pattex yellow ; mouth and inserts Araldite. For the Carman
Araldite + satured with Micro baloons . The glue in gel ; no good.
Fuselage
Sand papier 240 and 400 For the good géometrie use grade 180 OR 240.For the finish grade 400 to 500
2 Coats dope nitro cellulosique
Glass fiber 25 grs (1 oz / m2)+ Epoxy. This is no more heavy and japan paper 20 grs+ 5/6 Coats dope.
This finish is better and more resistant in the years.
The wing and Stabizer
Sand paper 240 400
2 coats dope
Covering with Polyspan médium 20 GRS/M2 (3/4 OZ) + 12 or 20 grs Japan paper
5/6 Coats dope nitro cellulosique
Technique liste

    Wing span 1600 - 63 inches

    Lengts 1240 - 48 ,8 ins

    Wings Aera 46 dm2 71,3 SQ/IN

    Stabilo Aera 10 dm2 15,5 SQ/IN

    Noze length 270 1O,6 ins

    Lever Arm 485 19,09 ins

    Breitness wing 270 + 80 Flaps 10,6 +3 1/8

    Weigth scare/dm2 43 grs

    Wegth modele 1980 grs

    C G 80 mm from BA 3 1/8 INS

    WING +FLAPS only wood 320 GRS with covering, no color 480 grs

[Air Ministry .]

wots the plane ?

[Guy Markham]

One could get the same induced drag advantage by increasing aspect ratio of a trapezoidal wing a bit, but we don’t, because we fly planes with aspect ratios that are about optimal.

How about this.. Sharkfire...  Combo of Shark 45 and Clip wing spitfire 

[PJ Rowland]

The answer is clearly here.

"I used to have the same problem that I think you have*, that is, that solving a series of theoretical engineering and design problems will result in success - when the problems were far more prosaic matters of trim, power, and practice. "

Alas if I could ever bang home a point its this is FAR more of the driving force in success that any design iteration.

I know its hard if not impossible to fathom, that most designs have to some degree "peak envelope performance" and there are maybe 15 people on the planet who can get a plane into proper trim to push the airframe beyond these limits.

Its easy to go along the path of "a new design concepts" adopting new ideas and engineering solutions in an attempt to gain an advantage.

The reality is, what determines a solid flight capable of high scores, has LESS to do do with the design parameters and more to do with the pilots ability to fly it accurately, which at the end of the day is a "trim and power delivery solution" based system .

Part of the reason Brett has flown the same setup essentially for 3 decades is the same reason Howard is flying a design virtually 30 years old. Its NOT because they arent smart enough to come up with something better, they are smart enough to understand the wheel doesnt need to be reinvented.

Igor has done HUGE amounts of investigation into stunt design much of it without any influence from the USA scene, mostly through understanding of what NEEDS to occur within the flight envelope.

There isnt a HUGE difference between what solutions Igor came up with and how systems like the Infinity down to Impact also achieved. 
The point is.. when multiple people arrive at virtually the same conclusions over 30 years and 80,000 flights, and many of THOSE people are saying the same thing, trim and power are key..

The reasons are because, whilst its fun to postulate over hoping to find something new that will change the game, the reality is, practice WAY more and this will overcome virtually any design improvement you may or may not find.


Its not wise to adopt the stance "these guys are stuck in past technology"  Its better to listen to sound advice and be steered in the correct direction, than to chase advantageous design solutions that may or may not result in 1/2 a total point improvement.